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An impulse travels along the pre-synaptic neurone, and when it reaches the axon ending it stimulates calcium channles to open on the pre-synaptic membrane. This allows calcium ions to rush into the neuron...

Enzymes are proteins. They are biological catalysts, meaning they increase the rate of reaction without being used up or changed. Different enzymes have different optimum temperatures and pHs, depending o...

A 'non-specific' defence system means that its response is the same for every invader (pathogen). In the human body this includes:

Skin- a physical barrier between the outside worl...

Both sperm cells and egg cells contain a haploid nucleus, this means that they contain half the number of chromosomes of a normal diploid cell. This is so that when the egg is fertilised by the sperm ther...

An action potenial reaches the synaptic bouton causing depolarisation which opens calcium voltage gated channels. Calcium moves into the cell and causes the movement of vesicles containing acetylcholine t...